Master alloy comprising zirconium and magnesium for use in making magnesium-base alloys containing zirconium



Patented Dec. 29, 1953 MASTER, ALLOY COMP AND MAGNESIUM F MAGNESIU ZIRCONIUM RISING ZIRCONIUM OR USE IN MAKING -BASE ALLOYS CONTAINING William P. Saunders and Frederick P. stricter,

Midland, Mich, assignor Company, Midland, Mi

Delaware 5 to The Dow Chemical b., a corporation of No Drawing. Application December 8, 1951, Serial No. 260,776

6 Claims. (01. 75-135) The invention relates to methods of making magnesium alloys containing zirconium. It more particularly concerns the production of a master alloy containing both magnesium and zirconium in more or less equal proportions which is suitable for use in the production of magnesium-base alloys containing zirconium.

The zirconium metal commercially available alloys with magnesium but slowly and to a limited extent and is not generally used in making magnesium-base alloys containing zirconium. Instead a master alloy of magnesium and zirconium is preferably formed by reacting the molten magnesium with zirconium tetrachloride. The zir conium tetrachloride becomes reduced by molten magnesium to metallic zirconium according to the reaction expressed in the following equation:

Limited amounts of CaClz and MgClz may also be present in these mixtures. By employing about 1 as much zirconium tet rachloride as magnesium in the reduction, a socalled master alloy is obtained containing more or less equal amounts of zirconium and magnesium and some entrapped by-product magnesium chloride, the rest of the saline constituents being removable from the metallic reaction mass by decantation and squeezing the mass. The master alloy consists essentially of a matrix of a magnesium-zirconium alloy, which is magnesium more or less saturated with zirconium (i. e. containing up to about 0.5 per cent of Zr), throughout which matrix is dispersed particles of zirconium metal comprising about 50 per cent by weight of the mixture. The amount ofby-prod uct magnesium chloride entrapped in the master alloy after decantation and squeezing is about 5 to 7 per cent of the weight of the master alloy.

In forming magnesium-base alloys containing zirconium by adding the so-prepared master alloy to melts of magnesium, there is danger of the molten magnesium undergoing such alloying of being blown about due to the violence with which the mastor alloy may react with melts of molten magnesium. This violence of the reaction, we have found, appears to be due to the magnesium chloride which is entrained in the master alloy during manufacture. Our investigations have shown that some of the entrained magnesium chloride, present in the master alloy, absorbs an amount of moisture from the ambient atmosphere prior to use which is dangerous to bring into contact with melts of molten magnesium as in making magnesium-base alloys with the master alloy. Such absorbed moisture on being brought into contact with molten magnesium, as in the alloying operation, produces a violent explosive-like reaction w ich causes more or less of the molten magnesium to be spattered about in dangerous manner. A peculiarity of this phenomenon is that it may not occur with every piece of the master alloy nor until the master alloy is well submerged below the surface of the molten magnesium to which the alloy is added, thus accentuating the hazard of the alloying operation. The danger of explosive-like reactions is greater the longer the lapse of time following manufacture of the master alloy.

We have now discovered that the foregoing dangers of alloying the magnesium-zirconium master alloy with melts of magnesium may be completely overcome by subjecting the master alloy to a puddling operation with a molten saline Washing flux comprisin one or both of the alkali metal chlorides, NaCl and P181. If desired, barium chloride maybe included in the washing flux but not in excess or" per cent of the weight are maintained at a temperature at which the magnesium alloy portion of the master alloy is molten as well as the flux constituents. On thus melting the master alloy along with the washing flux, and paddling these materials together, the flux entrain-ed in the master alloy is released and absorbed by the washing fiux forming a mixture of spent washing flux containing the magnesium chloride released from the master alloy. A sufficient amount of washin flux is used so that the magnesium chloride concentration in the spent flux mixture, formed in the puddling operation, is below about per cent by weight. The spent flux mixture resulting from the puddling operation is separated from the resulting treated master alloy as by decantation and squeezing. The master alloy so separated from the spent washing flux is cast in a suitable mold and thereafter may be used in making magnesiumdiase alloys containing zirconium without danger of explosions or undesirable boiling, spattering, and the like.

The washing flux is preferably thinly fluid at operating temperature and the desired fluidity is achieved making the flux of two or more of the proper chlorides so that the melting point of the flux mixture is preferably below about 1350? E, although saline fluxes melting as low as 900 F. and as high as 1480 F. be used that do not contain significant amounts of a hygroscopic alkaline earth metal chloride exclusive of Ba-Clz.

Examples of suitable saline fluxes for use according to the invention are set forth in the following table in parts by weight together with the approximate temperature at which the flux is liquid.

1 Flux constituents Temperature at which flu is liquid, C.

l Flux No. I 1

in washing the master alloy with the washing flux, the master alloy may be heated, as in an open melting pot, to a temperature above its melting point along with about an equal weight of washing flux. The washing flux melts and serves to protec the melt from attack by the air during the melting and washing operation. The

molten washing flux and the molten master alloy are together so as to permit the washing flux to absorb and dilute the salines entrapped in the master alloy as made and released on being melted. iew minutes of stirring of the molten washing after, the mixture is left to settle whereby the spent washing flux rises to the top of the molten metal which collects at the bottom of the melting vessel. The spent flux is separated from the molten metal as by decantation. If desired, the washing operation may be repeated once or twice.

The following example is illustrative of. the practice of the invention;

Example A conventional master alloy is formed by melting 19 pounds of magnesium, heating the molten metal to 14cm F., and mixing with the molten metal 85 pounds of a mixture of equal parts of ZYCL} and X01. In the reaction which ensues the ZrCh is reduced to metallic zirconium forming magnesium chloride as a icy-product. Part of the zirconium so-produced alloys with the balance of the molten magnesium i hile the .remain and mast-er alloy suirlces. Thereder or the zirconium becomes dispersed in the magnesium-zirconium solution along with about '7 per cent by weight of lay-product MgClz thus forming the conventional master alloy containing about equals weights of magnesium and zirconium. The conventional master alloy settles under the supernatant layer of molten KCl containing the balance of the icy-product MlgClz: which is not entrained in the master alloy. The settled conventional master alloy so or o herwise produced is subjected to washing according to the invention. The supernatant layer of molten KCl and MgClz is skimmed. off and about 2 pounds of the master alloy is withdrawn from the fluxfree surface of the molten mass thereof by dipping with a ladle. The so-reuioved master alloy is added to and mixed with a molten washing flux consisting of a melt of 15 pounds of BaClZ and 15 pounds of KCl at l lili) F. The mixing is con-- tinued for 3 minutes. The resulting washed master alloy isseparated from the spent washing flux and. solidified in an iron mold. Analysis of the so-obtained master alloy shows that the entrained MgClz content is reduced toibelow 0.5 per cent. The solidified master alloy is put into storage. After storage for 3 days the master alloy is added to a melt of a magnesium-base alloy consisting of 95 pounds of magnesium and 5 pounds of zinc, melted in an open melting pot, thereby forming a magnesium-base alloy containing about 5 per cent of zinc and about 0.5 per cent of zirconium. The alloying takes place without any violence of reaction and with an e ciency of about per cent. In contrast, when a similar amount of the conventional unwashed master alloy, after 3 days of similar storage, is added to and mixed with the same magnesiumbase alloy under the same conditions in a similar melting pot there ensues an explosive reaction ejecting molten metal from the melting pot.

The term magnesium-base alloy as used herein includes magnesium and alloys thereof in which the magnesium content is at least per cent by weight.

We claim:

1. The method oi making a master alloy comprising more or less equal amounts of magnesium and zirconium for alloying with magnesium to make inagnesium base alloys containing zirconium and at least 80 per cent of magnesium which comprises reacting a saline flux mixture comprising alkali metal chloride and zirconium tetrachloride with an excess of magnesium at a temperature between 1309" and 1453" C. so as to reduce the zirconium. tetrachloride to metallic zirconium and produce magnesium chloride as a by-product, said metallic zirconium becoming entrained in the said excess of iiagnesium as a master alloy, withdrawing at least a portion of the so produced master alloy and mixing it with a saline Washing flux comprising an alkali metal chloride selected from the group consisting of sodium chloride and potassium chloride at a temperature at which both the said washing four and master alloy are molten so as to release tilC entrained magnesium chloride from mas" alloy and absorb the released magnesium chloride in the said washing flux, and separating the sctreated master alloy from the resulting flux mi ure.

2. Themethod according to claim 1 in which the saline washing fiuxcontains barium chloride in amount not over 80 per cent of the washing flux.

3. The, method according to claim 1 inv which the saline washing flux comprises sodium chloride.

4. The method according to claim 1 in which the saline washing flux comprises potassium chlo ride.

cent by weight of the flux.

WILLIAM P. SAUNDERS. FREDERICK P. STRIETER.

6 References Cited in the tile 01' this patent UNITED STATES PATENTS Number Number Name Ball et a1 Ball et a1.

FOREIGN PATENTS Country Great Britain Great Britain Date Feb. 14, 1950 Feb. 14, 1950 Date Feb. 10. 1941 June 4, 1949 

1. THE METHOD OF MAKING A MASTER ALLOY COMPRISING MORE OR LESS EQUAL AMOUNTS OF MAGNESIUM AND ZIRCONIUM FOR ALLOYING WITH MAGNESIUM TO MAKE MAGNESIUM-BASE ALLOYS CONTAINING ZIRCONIUM AND AT LEAST 80 PER CENT OF MAGNESIUM WHICH COMPRISES REACTING A SALINE FLUX MIXTURE COMPRISING ALKALI METAL CHLORIDE AND ZIRCONIUM TETRACHLORIDE WITH AN EXCESS OF MAGNESIUM AT A TEMPERATURE BETWEEN 1300* ANF 1450* C. SO AS TO REDUCE THE ZIRCONIUM TETRACHLORIDE TO METALLIC ZIRCONIUM AND PRODUCE MAGNESIUM CHLORIDE AS A BY-PRODUCT, SAID METALLIC ZIRCONSIUM BECOMING ENTRAINED IN THE SAID EXCESS OF MAGNESIUM AS A MASTER ALLOY, WITHDRAWING AT LEAST A PORTION OF THE SO-PRODUCED MASTER ALLOY AND MIXING IT WITH A SALINE WASHING FLUX COMPRISING AN ALKALI METAL CHLORIDE SELECTED FROM THE GROUP CONSISTING OF SODIUM CHLORIDE AND POTASSIUM CHLORIDE AT A TEMPERATURE AT WHICH BOTH THE SAID WASHING FLUX AND MASTER ALLOY ARE MOLTEN SO AS TO RELEASE THE ENTRAINED MAGNESIUM CHLORIDE FROM THE MASTER ALLOY AND ABSORB THE RELEASED MAGNESIUM CHLORIDE IN THE SAID WASHING FLUX, AND SEPARATING THE SOTREATED MASTER ALLOY FROM THE RESULTING FLUX MIXTURE. 